No studies have directly examined the role of social and sexual networks in maintaining the high rates of sexually transmitted diseases (STDs) among African-American adolescents. The goal of the proposed five-year longitudinal study is to develop a better understanding of the role of social and sexual networks in maintaining the high prevalence of STDs among African-American adolescents residing in the Bayview-Hunters point area of San Francisco. We will accomplish this by interviewing a random digit telephone sample of African-American adolescents, 14-19 years old, residing in San Francisco, CA and testing them for STDs. In addition, we will recruit and interview their sex partners in order to characterize the index adolescents' social and sexual networks. Ultimately, the findings of this study may permit public health programs to focus part of their resources on those individuals who are essential to the spread of STDs, and by doing so, to quickly and cost-effectively slow the spread of STDs among adolescents. Specifically, our goals are: 1. To determine the association between the characteristics of adolescents' social and sexual networks and the incidence and prevalence of STDs among 240 African American adolescents in the San Francisco metropolitan area over a two year time period. 2. To determine behavioral and developmental factors associated with membership in STD risk-related social and sexual networks among 240 African American adolescents in the San Francisco metropolitan area over a two-year time. 3. To determine the accuracy of adolescents' perception of risk for STDs among 240 African American adolescents in the San Francisco metropolitan area by comparing their risk perceptions to their proximity to or membership in STD risk-related social and sexual networks over a two year time period. 4. To determine behavioral and development factors associated with membership in STD risk-related social and sexual networks among African American adolescents in the San Francisco metropolitan area who have recently become active.